Buggy code:
public class FileSystem implements INameEnvironment , SuffixConstants { public interface Classpath { char [ ] [ ] [ ] findTypeNames ( String qualifiedPackageName ) { } NameEnvironmentAnswer findClass ( char [ ] typeName , String qualifiedPackageName , String qualifiedBinaryFileName ) { } NameEnvironmentAnswer findClass ( char [ ] typeName , String qualifiedPackageName , String qualifiedBinaryFileName , boolean asBinaryOnly ) { } boolean isPackage ( String qualifiedPackageName ) { } List fetchLinkedJars ( FileSystem . ClasspathSectionProblemReporter problemReporter ) { } void reset ( ) { } char [ ] normalizedPath ( ) { } String getPath ( ) { } void initialize ( ) throws IOException { } } public interface ClasspathSectionProblemReporter { void invalidClasspathSection ( String jarFilePath ) { } void multipleClasspathSections ( String jarFilePath ) { } } public static class ClasspathNormalizer { public static ArrayList normalize ( ArrayList classpaths ) { } } FileSystem . Classpath [ ] classpaths ; Set knownFileNames ; public FileSystem ( String [ ] classpathNames , String [ ] initialFileNames , String encoding ) { } FileSystem ( FileSystem . Classpath [ ] paths , String [ ] initialFileNames ) { } public static FileSystem . Classpath getClasspath ( String classpathName , String encoding , AccessRuleSet accessRuleSet ) { } public static FileSystem . Classpath getClasspath ( String classpathName , String encoding , boolean isSourceOnly , AccessRuleSet accessRuleSet , String destinationPath ) { } private void initializeKnownFileNames ( String [ ] initialFileNames ) { if ( initialFileNames == null ) { this . knownFileNames = new HashSet ( 0 ) ; return ; } this . knownFileNames = new HashSet ( ( ( initialFileNames . length ) * 2 ) ) ; for ( int i = initialFileNames . length ; ( -- i ) >= 0 ; ) { char [ ] fileName = initialFileNames [ i ] . toCharArray ( ) ; char [ ] matchingPathName = null ; final int lastIndexOf = CharOperation . lastIndexOf ( '.' , fileName ) ; if ( lastIndexOf != ( - 1 ) ) { fileName = CharOperation . subarray ( fileName , 0 , lastIndexOf ) ; } CharOperation . replace ( fileName , '\\' , '//' ) ; <START_BUG> for ( int j = 0 ; j < ( classpaths . length ) ; j ++ ) { <END_BUG> char [ ] matchCandidate = this . classpaths [ j ] . normalizedPath ( ) ; if ( ( ( ( this . classpaths [ j ] ) instanceof ClasspathDirectory ) && ( CharOperation . prefixEquals ( matchCandidate , fileName ) ) ) && ( ( matchingPathName == null ) || ( ( matchCandidate . length ) < ( matchingPathName . length ) ) ) ) matchingPathName = matchCandidate ; } if ( matchingPathName == null ) { this . knownFileNames . add ( new String ( fileName ) ) ; } else { this . knownFileNames . add ( new String ( CharOperation . subarray ( fileName , matchingPathName . length , fileName . length ) ) ) ; } matchingPathName = null ; } } public void cleanup ( ) { } private static String convertPathSeparators ( String path ) { } private NameEnvironmentAnswer findClass ( String qualifiedTypeName , char [ ] typeName , boolean asBinaryOnly ) { } public NameEnvironmentAnswer findType ( char [ ] [ ] compoundName ) { } public char [ ] [ ] [ ] findTypeNames ( char [ ] [ ] packageName ) { } public NameEnvironmentAnswer findType ( char [ ] [ ] compoundName , boolean asBinaryOnly ) { } public NameEnvironmentAnswer findType ( char [ ] typeName , char [ ] [ ] packageName ) { } public boolean isPackage ( char [ ] [ ] compoundName , char [ ] packageName ) { } }

Fix:
for ( int j = 0 ; j < ( this . classpaths . length ) ; j ++ ) {